L40- mass spectrometry

what is spectroscopy

it is how matter interacts with the electromagnetic radiation- theory

what is spectrometry ?

its the application of of spectroscopy to produce results- practical

what is a spectrometer

its the instrument used to measure spectroscopy

what are the two things that need to happen to a molecule for mass spec

• the molecule needs to be ionised

• the ions need to be separated

what does m/z mean

m= the mass of the ion

z= the charge of the ion

together they are considered the mass of the ion

describe electron ionisation

electron ionisation( electron impact )

• hard technique

• generates a radicle cation or anion

• usually results in lots of fragmentation ( daughter ions )

what is mass spec

its the analytical technique used to measure the mass of the charged ions

describe chemical ionisation

• soft technique

• generates ions through protonation to give MH⁺ or deprotonation M-H^-

• usually results in less fragmentation

describe how the separation of charged ions works

the ions put into a vacuum and allowed to be deflected and detected

deflection depends on the charge and the mass of the ion

what are the two different ways mass spec can be used to identify compounds

• HRMS/parent ion peaks - high resolution mass spec

• fragmentation patterns

what is the difference between exact mass and molecular mass + which is used in mass spec

• exact mass-the exact mass of single molecules

• molecular weight- the yield calculation, its calculated using average masses of isotopes

exact mass is used in mass spec

what is the nitrogen rule

it apples to all neutral molecules containing C,N,O,H and the halogens

they all have even molecular weights

but if they contain an odd number of nitrogen atoms then their molecular weight will be odd too